Nonsuppurative polyarthritis is an infectious condition of older, growing lambs (6–16 weeks old) characterized by high rates of disease and moderate to severe lameness with enlargement of affected joints.
Etiology of Nonsuppurative Polyarthritis in Lambs
The infectious agent of nonsuppurative polyarthritis, Erysipelothrix rhusiopathiae, is thought to infect the animal through wounds created as a result of shearing, tail docking, or castration. However, outbreaks can occur after bloodless procedures, particularly during extended periods of wet weather, which increases the level of stress and appears to enhance the infective organism's survivability in the environment.
E rhusiopathiae localizes in joints via hematogenous dissemination and infects the synovial membrane. Progression of the synovial infection results in synovitis and damage to articular cartilage and underlying subchondral bone.
Clinical Findings and Lesions of Nonsuppurative Polyarthritis in Lambs
Sudden onset of moderate to severe lameness in a high number of growing lambs suggests nonsuppurative polyarthritis. Lameness typically occurs in two or more limbs, and the joints most often affected are the carpus and hock.
Affected lambs are reluctant to move, and they spend extended periods of time in sternal recumbency. Growth is often severely stunted. Some lambs eventually develop chronic polyarthritis.
Progression of nonsuppurative polyarthritis results in proliferation of the synovial membrane, thickening of the joint capsule without substantial joint effusion, and eventual erosion of articular cartilage.
Diagnosis of Nonsuppurative Polyarthritis in Lambs
Sudden onset of lameness in a large number of growing lambs suggests polyarthritis due to infection by E rhusiopathiae. Because joint effusions are minimal, attempts to obtain a sample from affected joints for culture and other diagnostic tests might be unsuccessful.
Prevention and Treatment of Nonsuppurative Polyarthritis in Lambs
Vaccination, where the disease is a recurring problem
Strict antisepsis and hygiene for tail docking and castration
Penicillin
Vaccination against E rhusiopathiae should be considered on premises where nonsuppurative polyarthritis is a recurring problem.
Adopting strict antiseptic techniques and maintaining hygienic conditions for tail docking and castration are recommended precautionary measures; however, they might not prevent the condition. So-called bloodless methods of performing both procedures can decrease the chances of wound contamination, but outbreaks are still possible.
Administration of penicillin for 5 days is recommended for effective treatment of nonsuppurative polyarthritis. Administration of NSAIDs helps improve lameness.
Key Points
Older, growing lambs can suddenly develop moderate to severe lameness associated with E rhusiopathiae infection, known as nonsuppurative polyarthritis.
For More Information
Arthritis in Sheep. NSW Government, Local Land Services.
